Bacterial Soft Rot vs Blackleg in Potatoes: Symptoms, Diagnosis, and Treatment

During the 1940s, the world had just over three years to discover a solution to the looming food crisis. In the 1940s there was not much more than three years to find a solution to the impending food crisis in the world.

Bacterial diseases are a major impediment to the production of potatoes in the world, leading to a huge economic loss and undermining food security. Among them, there are two of the most devastating diseases of field crops and stored tubers which are known as bacterial soft rot and potato blackleg. Under favourable conditions, the diseases which are mostly caused by Pectobacterium species can cause yield losses of up to 20 percent and total crop failure.

Bacterial soft rot of potato has an economic impact that is beyond direct loss of the yield. When infected tubers contaminate healthy produce during transportation and storage in storage facilities, the facility experiences massive losses. These pathogens are known to spread very fast hence destroying the entire storage facilities into millions of dollars every year. To know how to treat bacterial soft rot and potato blackleg, one needs to identify it properly, with preventive measures and good management techniques.

The causative organisms which are mostly Pectobacterium species are common soil dwelling bacteria that can infect potato plants and tubers by exploiting wounds and natural openings. Effective measures to be taken in controlling bacterial soft rot cannot be done without proper identification. In the absence of proper diagnosis, farmers can use wrong treatment methods, which will continue to pressure the disease and cause loss of money.

This is an extensive manual on the biological control solutions on How to treat bacterial soft rot and blackleg in potatoes than with chemical treatments. Current bacterial soft rot control​ strategies offer environmental friendly sources and yet retain good effectiveness against these problematic bacterial parasites.

Knowledge of the Pathogens

The bacterial soft rot and blackleg pathogens have a complex nature and heterogeneous species composition as shown by their scientific classification. The bacterial soft rot scientific name includes the subspecies of Pectobacterium carotovorum subsp, which is the pathogen of soft rot. In the meantime, black leg potato is caused by Pectobacterium atrosepticum also known as, black leg potato which specifically attacks potato plants in colder growing environments.

These gram-negative bacteria have similar features, such as the generation of pectolytic enzymes which digest plant cell walls. The biological control of bacterial soft rot facilitates quick maceration of tissues and they give rise to the typical soft and wet decay characteristic of these diseases. The pathogens grow best in damp, warm climates and are able to survive in soil and plant litter over long periods of time.

Bacterial Soft Rot: Presentation and Diagnosis

Infection in bacterial soft rot potato is characterized by small water-filled lesions on the tuber surfaces especially at the lenticels and wounds. These are the symptoms that are not usually noticed until the disease reaches its advanced stages. The disease causes the affected tissue to be soft and wet in nature and has a distinctive coloration of cream to tan which makes it distinguishable among other diseases in potatoes.

Advancing tissue erosion forms a distinct line of demarcation between the healthy tissue and the diseased tissue. This clear delimitation is one of the diagnostic characteristics of the bacterial soft rot and blackleg in potatoes symptom. The affected tissue becomes soft and can be easily detached by the healthy parts.

Additional diagnostic indicators are the odor characteristics. Infections that occur early are usually odorless, though with an invasion by secondary organisms in the affected tissue, foul, putrid odors develop. This characteristic smell tends to warn farmers of storage issues even before the manifestation of the symptoms becomes rampant. In the coming sections, we will discover how to treat bacterial soft rot and blackleg in potatoes.

Blackleg Disease: Characteristics and Blackleg of Potato Symptoms

The symptoms of potato blackleg are unique and cannot be confused with the symptoms of soft rot, although they may co-exist. Premature emergence is also characterized by retarded growth and chloric foliage which attains a typical yellowish look. Blackleg is diagnosed by the common name "inky black" stem base decay and this is used as the main field identification feature.

Blackening of pith tissue internally commences at the bottom of the infected stems and extends upwards giving a dark and watery look on the stones cut along the grain. Symptoms of foliage determine the development of vascular dysfunction and water stress through the change of yellowing of the foliage to upward-rolling foliage margins.

The symptoms of blackleg of potato come in two different ways: early blackleg soon after the emergence and late season blackleg to the mature plants. Early infections are usually fatal to the plants or cause severe stunting and late infections can also enable plants to survive with a lesser yield potential.

Bacterial Soft Rot and Blackleg in Potatoes Symptoms and Differentiating

The correct diagnosis cannot be made without the systematic visual symptom examination accompanied by some laboratory confirmation method. The bacterial soft rot control is related to the proper identification of the pathogen because treatment plans are different in different causative organisms.

The methods of laboratory diagnosis start with isolation in nutrient agar plates in which characteristic colonies of bacteria grow in 24-48 hours. Preliminary identification of bacterial pathogens is done using biochemical tests such as catalase, oxidase, and gram staining. These conventional microbiological tests can be used to verify the bacterial soft rot scientific name.

Crystal violet pectate (CVP) medium provides particular confirmation to pectolytic bacteria that cause the soft rot and blackleg diseases. The positive results show that enzymes needed to degrade pectin, which is one of the main peculiarities of these pathogens.

Bacterial Soft Rot Control Solutions

Biological control of bacterial soft rot has numerous benefits over conventional chemical control- it is non-toxic, less resistant is developed and it is compatible with organic farming. Novobac has developed products such as Bactonus which take advantage of useful microorganisms to reduce the harmful ones in the crops in a sustainable manner.

The biocontrol agents like Bacillus velezensis present in Bactonus are effective in the production of antimicrobial compounds which inhibits the growth and dissemination of harmful bacteria i.e. bacillomycin, iturin and surfactin. The beneficial bacteria also enhance the natural defense mechanisms of plants making them resistant to infections.

Bactonus (Novobac product) is a specific bacterial wilt and soft rot disease preventer that does not cause harm to the beneficial soil organisms. It promotes root and shoot development which contributes to the overall plant development and productivity. It is a biofungicide that is a sustainable option consistent with the current green farming activities.

Equally, Bacillus velezensis formulations are offering satisfactory microbial-based control, which augments the already existing cultural and chemical methods of disease management. These biocontrol products are a future-proof method of controlling bacterial soft rot in a sustainable and ecologically friendly way by promoting soil fertility and prophylaxis of diseases over the long run.

In short, the adoption of biocontrol products such as Bactonus can be used to take advantage of natural biochemical interactions to have healthier crops and safer farming ecosystems.

How to treat bacterial soft rot and blackleg in potatoes: Interwoven Management Strategies

Bacterial soft rot management involves holistic integrated measures that involve both cultural, biological, and chemical control. bacterial soft rot control starts with the pathogen-free seed tubers because infected planting material is the main source of inoculums to cause infections in the fields.

Recommendations on field sanitation and crop rotation involve the removal of the infected plant debris, the control of volunteer potato plants, and the continuous use of the same fields to produce potatoes. Optimization of planting depth and spacing enhances air movement and minimizes the level of humidity which encourages the growth of bacteria.

Waterlogging conditions that cause bacteria multiplication and plant stress are avoided by irrigation management. Disease-favorable conditions in the environment are reduced by proper drainage systems and the scheduled irrigation time.

Prevention and Future Prognosis of Bacterial Soft Rot Potato

Biological control of bacterial soft rot is more cost-effective than curative treatment, and therefore proactive methods of management prove to be economic. Certified seed programs are also relevant in limiting the levels of inocula and also avoiding the introduction of diseases in new fields of production.

The breeding and biotechnology methods of developing resistant varieties are still being developed. Future research prospects in biocontrol are improved formulations, the use of better delivery mechanisms and wider spectrum antimicrobial activities.

Improved biocontrol preparations of bacterial soft rot of potato uses a combination of several useful microorganisms, which widen their control range and boost their stability in fluctuating environmental circumstances. The mechanism that underlies the biological control of bacterial soft rot is uncovered through studies on plant-microbe interaction that are applicable in formulating more effective control strategies.

The development of integrated pest management systems embraces the use of the biological, cultural, and chemical pest control strategies co-ordinated to control the pests. These systems maximize the control efficacy and reduce the environmental impact and the cost of production.

Reference:

• Koepsell, Paul A. "Controlling bacterial soft rot and blackleg of potatoes." (1978).
• Arora, R. K., and SM Paul Khurana. "Major fungal and bacterial diseases of potato and their management." Fruit and vegetable diseases. Dordrecht: Springer Netherlands, 2004. 189-231.